The present disclosure relates to a fixing device fixing a toner image on a medium and an image forming apparatus including this fixing device.
An image forming apparatus of an electrographic manner includes a fixing device thermally fixing a toner image on a medium.
For example, the fixing device includes a heating roller, and a pressuring roller pressured to the heating roller. The pressuring roller includes a cylindrical body composed of laminated rubber layers, and a shaft body penetrating the cylindrical body and supporting the cylindrical body via a bearing. Both ends of the cylindrical body are elastically supported by two first elastic supporting mechanisms, and both ends of the shaft body are elastically supported by two second elastic supporting mechanisms. Because the pressuring roller is supported at four points in a longitudinal direction, pressuring force of the pressuring roller to the heating roller becomes uniform in the longitudinal direction, and then, oblique conveyance and jam of a sheet are prevented.
Because the pressuring force of the pressuring roller to the heating roller is very strong in comparison with pressuring force of a pair of rollers for sheet conveyance, the shaft body supporting the heating roller may be slightly warped (bent). However, in the above-mentioned fixing device, warp of the shaft body due to the pressuring force is insufficiently considered. Accordingly, in the above-mentioned fixing device, the pressuring force does not become uniform in the longitudinal direction, and then, there is a program that winkles are caused in the sheet.
The above-mentioned problem may be solved by thickening the shaft body and increasing rigidity of the shaft body. However, because the heating roller is thickened if the shaft body is thickened, there is another problem that the fixing device is enlarged.